Two years ago, at the height of the Deepwater Horizon spill in the Gulf of Mexico, we learned how quickly our knowledge of oil extraction had outpaced clean-up technologies. And when the next oil spill hits, as it inevitably will, the best way to clean up might be a very simple one, albeit with a very high-tech twist. The solution might be to soak the oil up with a sponge–a carbon nanotube sponge, to be precise.
Researchers at Rice University in Houston have created flexible, reusable, carbon-nanotube sponges that are so light that they can absorb at least 10 times as much as a typical kitchen sponge, and are made of a material that will reject water in favor of oil.
Graduate student Daniel Hashim had been trying to make a battery supercapacitor by adding a touch of boron to his carbon nanotube recipe. But instead of the powdery substance he was expecting, what emerged was an airy, spongy, flexible foam block that resolutely held its shape. By including boron, he and his colleagues found that they not only caused the diminutive nanotubes to kink and bend but that they provided a way for the tubes to bond to each other. “The resulting material is a very airy foam. It’s the second-lowest density material in the world,” Hashim says. “Its volume is greater than 99% air.”
The nanotube sponges are so low density that they can suck up 120 times their own weight; a cellulose sponge soaks up about five to 10 times its weight, maximum. They’re also hydrophobic (water resistant) and oil absorbent, so they float and can act as a perfect filter to take up only oil while leaving water behind. They can be manipulated with magnets, can be scaled up into relatively large sizes, and can even act as a portable, lightweight storage tank. They can store the oil for as long as needed, then can either be wrung out to yield pure fuel, or burned to yield heat energy. And because of their elasticity and robust form, the same sponges can be used over and over again.
Hashim says he began the work three years earlier, before the spill in the Gulf. But our fossil-fuel loving society is clearly desperate for effective ways to clean up some of our dirtiest messes. Since his research was published, Hashim has already received numerous calls from oil companies in the U.S. and around the world, as well as a few water purification companies.